Hitherto, polyethylene terephthalate has been practically used as the material of a support for sheet-form photographic materials such as X-ray photographic films, lithographic light-sensitive films, etc.
Also, the use of inexpensive polyester series supports has been proposed in place of conventional cellulose series supports for roll films such as 35 mm negative photographic films.
However, because a polyester series support does not adhere to a photographic emulsion layer formed thereon as well as a cellulose series support, various subbing agents and surface modification by physical means have been proposed for ensuring good adhesion.
The reason that a polyester series support does not adhere to a photographic emulsion layer as well as a cellulose series support is not clearly understood. However, this difference in adhesion is considered to be due to the high crystallinity of the surface of the polyester series support that is generally formed from a biaxially stretched polyester film.
It is known in the art to form a subbing layer between the support and the photographic emulsion layer, or to physically modify the surface of the support, to thereby ensure the adhesion of a photographic emulsion layer to a polyester series support.
Known subbing agent for a polyester series photographic support include polyester series polymers, vinylidene chloride series polymers, acryl series polymers, SBR series polymers, and maleic acid series polymers, etc., as described, e.g., in Nippon Setchaku Gijyutsu Kyoukai Shi (Journal of Adhesive Technic Society of Japan), 23, 178(1987).
Known techniques for the surface modification of a polyester support by physical means include solvent etching ultraviolet irradiation, corona discharging treatment, flame treatment, glow discharging treatment, etc., as described, e.g., in J.Polym. Sci. Chem. Ed., 22, 419(1984), J. Applied Polym. Sci., 19, 3315(1975), Polymer, 18, 675(1977), and J. Material Sci., 14, 1344(1979).
These means are selected depending on the property of the photographic emulsion that is being coated on the support. Often, both physical surface treatment and a subbing agent are employed in combination.
In particular, in a photographic support comprising a polyester mainly containing polyethylene naphthalate, the combined use of physical surface modification and a subbing agent is essential. However, because the equipment is expensive and a complicated technique is required for physical surface modification, there is a need in the art to provide a polyester series support which only requires a subbing agent to provide the desired degree of adhesion.
The subbing agent is coated onto the support just before the entering a width-wise direction stretching machine or after issuing from a film making machine. However, the former system is frequently employed because adhesion of a subbing agent to a support is enhanced prior to stretching in the width-wise direction. The other reasons are that the coated layer can be dried in the oven of the width-wise direction stretching machine, the equipment can be simplified, etc.
In a roll type light-sensitive material such as a 35 mm photographic film, it is known that curling is retained by the film support caused by winding around a core. Curling a cellulose series support curling of the support is reversed in a developer due to its water-absorbing property, to thereby avoid development mottling. However, such curling cannot be reversed in a polyester series support, which in turn causes development mottling.
In order to solve the above described problem, a technique of annealing a polyester series support at a temperature of from about 5.degree.to 20.degree. C. lower than the glass transition temperature of the support material has been proposed to thereby impart curling resistance to the support as described, e.g., in JP-A-6-67346 (the term "JP-A" as used herein means an "unexamined published Japanese patent application"). The annealing treatment is preferably carried out before forming the coated layer on the support, namely, directly after the film-making step. The support is usually annealed in a rolled state for from 0.5 to 100 hours, and preferably from 10 to 30 hours.